2 Answers

3 votes

well -

Unlike in Generation I, Fissure can affect a Pokémon whose Speed stat is greater than the user's current Speed stat. However, it cannot affect a Pokémon of a higher level. The accuracy of Fissure depends on the level of the user and the level of the target and is worked out with the formula: Accuracy = ((level of user - level of target) + 30)%. Fissure ignores all changes to accuracy and evasion stats. bulbapedia

so its that or your using it on a flying type or a pokemon with levitate